Telephony.



TELEPHONY.

APPLICATION FILED 'JUNE 1o, 1912A v Patented Aug. 26, 1913.

` {SHEETS-SHEET 1.

E. R. GGRWIN.

TELEPHONY.

AVPPLHIATION FILED JUNE 10, 1912A 159g? l ,$2 1 2. v Patented Aug. 26, 1913.

Z SHEETS-SHEET 2.

'if EZ/Yew:

narran srArEs PATENT. orrion.

EL'LEB, B. CORWIN, OF CHICAGO, ILLIOIS, .ASSIG-NOR TO CORWIN TELEPHONE MANU-l v IFACT'UEIN G COMPANY, A CORPORATION OF ILLINOIS.

nowhere.

Specification of Letters Patent.

Patented Au g. ee, reis.

Original application filed April 24, 191,1., Serial No. 622,936. Divided and this application filed June 1o,

` 1912. Serial No. 702,730.-

To all whom i may concern Be it known that l, ELMER R. CoRwIN, citizen ,of the United States, residing at Chicago, in the county of Cook. and State o Illinois, have invented a certain new, and useful improvement in Telephony, (this application being a division of the application, Serial No. 622,936, filed April 24, 1911,) of which the following is a full,vclear, conoise, and exact description, reference being had to the accompanying drawings, forming' a )art of this specification.

IMy invention relates to telephone systems and in one of its kaspects embodies an 1nterior or intercommuni'cating system,r though it is to be understood that I do not limit this portion of my invention to systems located entirelv within buildings since it 1s possible to ellect intercommunication between the telephonesI of my intereomn'iunicating system whether such telephones are in the same building or in different buildings.

Some features embodied in my intercomimmicating system are adapted for use elsewhere and are broadly claimed.

My I ueseutapplication is a division of my application xSerial No. 622,936, filed April 24, 1911, the present case relating particularly to the intercommunicating system which was disclosed in that application in connection with exchange equipment provided with mechanism for auton'iatically effecting the extension of telephonedines.

l will explain my invention fully by reference to the accompanying drawings showing the preferred embodiment thereof, and in which- Y Figure l is a diagrammat" 1 view illust-ratinglr my improved intercommunicating system 'and certain apparatus foi-'holding the automatically selectable trunk line which is shown in Fig. 2.and ,which also diagram-f matically indicates certain well known' automatic telephone exchange v equipment,

though l do not wish .to limit myself to au-` tomatic exchanges.

Referring now to the intercommunicating system ofmy invention I have shown three stations each having lines extending to each ot' the other stations; embodiment of the inventi( e illustrated are metallic lines to which I di', hot Wish. to be limited. v line' l v1 extending therefrom to each of the The lines in theA Station Nori thus basa metallic" other stations, similarly station N o. 2 has a telephone line 2 2 extending to each of the other stations, and station No. 3 has a telephone line 3 3 extending to each of the other stations. it each station there are 'a number of liney selecting keys a, one individual to each line extending tofsuch station from another station, wherebyeach station may select any of the other stations, providing that the station to be'selected is free for selection.

Assuming that the party at some intercommunicating station, say at station No. l, desires communication with some other intercomm'unicating station party, say party at station No. 2', the Erst or calling intercommunicating station party will first remove his telephone receiver Z) from its switch-hook c vthereby bridging his telephone apparatus across his'line l 1, such bridge bemg traceable 4,from the upper-pole ot-the battery e through the impedance f o`t1 the calling line, the right hand armature switch of l or relay g and the normal contact of such armature switch, the transmitter 7i .by way of a dial switch mechanism t' (which is here employed to select a trunk line but. which should be replaced by a permanentconnection between said armature switch and transmitter if the provision for automatic selection of'trunk lines were absent), Vthe receiver b, the switch-hook e and the contact directly engaged thereby, theleft hand armature switch of relay g and its normaLcontact, a.secondimpedance f1 of the calling line to the lower tergninal of the battery e. This bridge is desiraily of' low resistance as compared with the resistance of theright hand winding of relay g by which characteristie another line seeking line No. 1 cannot theh causev the enrgization of the relay .g belonging to such line seeking line to the seeking line is necessary as will here-l mafter appear 1n order to enable a seeking No. l` which energizeation of such relay belonging i they now denergized electromagnetv line to be telephonicallyconnected with line sought, such energization taking etl'ect when said'w right handwinding of relay f7 belonging to a seeking 1i eis bridged across' the idle line being sough there then being no low shunt across the selected or called line, the transmitter tion of such idlefline being in open or and I receverat the -stalceiver and transmitter thereat will enable the manifestation of a busy test signal in the telephone receiver at another' station that might be seeking the first calling line. The calling part yhaving placed his telephone in bridge of t c line for the purposes stated, and later more fully to be explained, next fully depresses the selecting key c individual to the line of the party being called whereby the latch member /c is fully depressed owing to the engagement of the pin c1 with the inclined portion of the key c, such movement of' the latch member 7c incidentally freein with tue associated key plungers to enable the springs associated with any previously depressed key to restore the same to its initial position in which the pin c1 is engaged with the key notch that is located nearest the key springs. This restoring movement of a previously actuated key occurs each time any selecting key is depressed sulliciently to carry the pin al below the points of the notches next adjacent and to the right i of the pins. 'The latch member f; carries two pins k1 ,7a2-located above contact springs 7c c,l the pin In* being closer to the spring 7c3, than is, the pin is with reference to the Spring k. As the latch member 7c is moved downward one circuit is first establishedbetween the spring k3 and its lower or alternate contact, and thereafter another vcircuit is established between the spring le* and its lower or alternate contact. The first circuit includes the right hand high resistance coil of relay g, which coil may have a resistance7 say of G-ohmsy and .which circuit maybe traced from the upper pole ofthe battery c through the impedance f of line 2, the two uppermost contacts of the actuated key o, that key at station No. '2 which is individual to'line No. 2, the said right hand high resistance winding of relay: g, contact s ring lc and its alternate Contact, the two ower contacts of said actuated key, the impedance.

i of line No. 2, to the lower pole of the battory e. If the telephone at the-called station No. 2 is upon its hook then the bridge coni taining the same, which is say 50 to 100 ohms when closed, is not established across the called line so that the high resistance right hand coil of the relay g at the calling station is not shunted by any low resistance path at the called station whereby the current from the battery ispermitted to flow in suiicient i volume through said right hand high resistance coil o the relay g, whereby the core of said coil 1s ei'l'ectively energized and the three armature switches associated with said core are operated. to establish circuits that will be traced follows: One circuit may be traced from the upper pole of the battery e the other pins o1 from engagement.

ithrough the ,impedance f of the calling line, the two uppermost contacts c1 of the switchhook c, the left hand coil ofthe` relay g at the calling station No. l (which lefthand coil may have a. resistance of say 5() to 100 ohms) the intermediate arniature switch of said relay, the spring 7st and its normal contact (the actuated selectinnr key now being released to permit the pin (1,1 to be bottomed.

in the notch nearest the key-head),.the impedance f1 of the calling line to the lower pole of the battery c. lVhen the selecting .key o has been released sufficiently to occupy its intermediate position, the circuit includin g the right ha nd coil of the relay g at station No. l is opened by reason of the separation of the spring /ci from its alternate Contact, but owing to the relationship of the springs k3 7c* with the pins d k2 the circuit through the lett hand coil oi said relay-is closed before the circuit through the right hand coil is opened during the restoring movement ot the actuated selecting key whereby the core common to the coils of the relay holds the arn'iaturc switches in their positions. The relay f/ at the calling station is now included in a circuit that contains the uppermost contact c1 of the switch-hook e at the calling station whereby the now only cffective circuit for said relay is broken when the receiver at the calling station is restored to'its switch-hook. The low resistance winding of the relay at the-calling station is included in bridge of the calling line to take the place of the bridge previously established at'the calling station through the transmitter and receiver thereat, but which latter bridge has beenopened by the attraction of the right hand armature switch, this latter bridge dependingupon said armature switch and its normal contact for its continuity when the associate receiver is oil' its hook. When the right hand armature switch of the calling station relay is attracted no high resistance winding of the relay at 'any station seeking' connection with line No. l may become energized owing to the shunting action of said low resistance relay winding at.4 the first calling station whereby the second calling station cannot secure telephonicconnection with line No. 1'. Another circuit established as a consequence of the energization of the relay at the calling station may be traced from theiupper terminal of the attery e through the impedancel f of the called lineNo. 2, .the upper contact of the actuated 4selecting key at station No. 1 which is individual to line No. 2, the right Ill hand armature switch. of the relay at the calling station and its alternatexintact, the

connection between said armature switch and i the transmitter l1, (Whether such connection is permanently continuous or is normally made through a circuit-breaker i), the receiver b at the calling station, the switchbridge ofthe cal giornale hook fc at=the-calli armature switch of t e callingstation relay, the contactv springlc3 Land its normal'contact,

key, the impedance pole-ofthe battery e. Infthis'way the calling station telephone Aapparatus .is supplied with talking battery yand is transferred to a bridge-comiectionfvbetween the sides ot the called line, 'this transfer occurring immediately'upon-theireleasefof the actuated selecting key to permit 'said key to occupy its intei-mediate position at which time the low resistance Windin of said relay is placed in ing line for the purposes previously stated. -If the called party lat station No. 2 -lias his 4telephone in use, a5 would have;

characteristic testing current flowed througlithe telephone receiver at calling station No. 1 duringthe .time that the selecting key was fully depressed'and which testing current would have found a circuit similar to thatcircuit uwhich -will hereinafter be described in connection with the telephone recervervat station No. 3 where C11-cuit connections are shown that arise When a .party seeking connection with a line across which a telephone bridge is established or the substitute -forfsuch `bridge that includes the left'hand low `resistance winding of the relay g at the busy station being sought.l

The calling party at 'station No. 1 receiving no busy test signal, depresses his ringing key l and thereby includes the signal or bell fm, at the called station in circuit with a ringing battery "it, which. circuit may be traced from the upper pole of said ringing battery through the contacts of the ringing key l, the lowermost contacts of the semirelcascd selecting-key, at station No. l, the lct't hand armature switch of the relay q at called station No. 2 and the normal Contact ol' such switch, the switch-hook c -at the called station and itsnornial contact, the sig- ,vnal receiver m at the called station, thence to tlic lower pole of said ringing battery.

lThe party at station No. 2 removes his telephone receiver from its switch-hook, in response to the signal conveyed by the device m, and connects his transmitter and receiver in bridge of the line No. 2, whereby the transmitter at station No.' 2 is battery current and telephonie'connection is established with the calling partys telephone previously bridged across line No. 2, it being understood that the calling partys telephone bridge across line No. v2- guards line No. 2 againstfselection by and permitting a test signalto be furnished to a second calling line seekingconnection with line No.'

2. It is understood that the called lpartys relay f/ remains inert throughout the entire connection as the system is here organized.

station, the yleft 'hand supplied with receiver at station No. 1 is in bridge of the line belonging to this station when the party there initiatesa call and prior to the actuation by another calling party. It has also. n

been explained how the calling partys telephone is placed in bridge of the called line i and how a low resistance'bridge including thefleft hand winding of the relay g at the calling station is substituted ,-for the telephone receiver bridge'that has been transferred from line No. l to line No. 2 Whereby line No. l is still guarded against selection by another` calling party. It will be understood that owing to the transfer of the calling partys' receiver tq a bridge connection between the sides 2 2`of the called line, such called line is guarded by such receiver bridge. When the parties are through conversation they restore their telephone receivers to their switch-hooks, Abattery e being excluded from circuit with the transmitter la at the called station No. 2 and also being excluded from circuit with the transmitter i, at the calling station. The only-circuit that previously remained closed lfor the relay g at callingstation No. 1 is opened at the switch-hook at the 'calling station when the telephone receiver tliereat 4restored thereupon. The equipmentsat both calling and called stations are now restored to ncr- .mal `so that eitherstation may call or be selected.

I will vnow describe theV testing circuit 4which prevails when the vcalling line seeks another line across which a low resistance bridge conductor has been placed either by the placing of a telephonereceiver circuit across the line or a circuitof equivalent resistance, namely, the left hand low resistance Winding of. a relay g at another calling station. The equipment at station No. 3 is shown in the "condition which ithas when the party at such station seeks'connection with the line across which one of the described low resistance bridges has been placed. By way 0f example, the' part-y at lic station No. 3 is shown in the act of eni dcavoring to select station No. l which was previously described as being a station calling station No. 2. The party at station N o. 3 removes his telephone from its switch-` hook and thereafter fully deprcsses theselecting key a individual to'line No. 1., be-

longing to station No. 1 and causes the cs-I tablishmcnt of al circuit that may be traced from the upper pole of the battery c, the impedance f of line No. l., tlie uppermost contacts of the actuated luy' at stal ion No. il, the'right hand winding No. 3, spring 7c at station No. 3 and the alternate contact of such spring, the lowermost contacts of the actuated key at station It has been explalned how the. telephone No. 3, the impedance j" of li-e No. 1, tc/tlie of relay g at stationv lower pole of the battery e. Owing to the presence of the low resistance bridge across line No. 1 the relay g at station No. 3 will not be sutiicient-ly energized 'to cause the operation of its armature switches. The party at station No. 3 also receives a busy test manifestation owing to the 4establishment of a circuit which may be traced from the ripper pole of the battery e, the impedance f ot line No. 3, the right hand armature switch of relay g at station No. 3 and the normal contact of such armature switch, the connection that intervenes bet-Ween said armature switch and the transmitter at station No. 3, the telephone receiver bl at station No. 3, the switch-hook at said station, the left hand armature switch ot' relay 17 and the normal contact of such switch, the busy test contact spring t"x and its alternate contact, thence to the lower pole of the battery e by way of the .device 0 for causing such modification of the current owing from the battery e as to produce a characteristic testing current to inform seeking parties of the busy condition of the lines. The apparatus at the different inter communicating stations is thus similar in equipment, function, arrangement and circuit association and similar parts are given similar characters ot reference.

ln Fig. 1 station No. 1 is not shown being a callingstation with reference to station No. 2 though station No. 3 is shown as being a calling station with reference to station No. 1. Station No. 1, however, is shown being in calling or selecting relation with a trunk line leading to the automatic exchange shown in Fig. 2, and I will now describe the operations, the Lapparatus, and circuit changes which occur when the party at an intercommunicating station seeks connection by means of ar trunk line with a party whose line extends to an au tomatic exchange, each of the intercommunicating stationsbeing preferably equipped with apparatus whereby that connection with such trunk lines may be effected, though I do not wish to belimited to the number of stations that may thus become connected with such trunk lines nor tothe association of such 'trunk lines'with intercommunicating stations in all embodiments of the invention As I have shown in my invention, a plurality of trunk lines extend to eachof the inter'cornrnunicatingstations, selecting keys being providedat each intercommunicatmg station. one individual to each trunk line'ateaeh intercommunicating station. I

have shown portions of two trunk lines g g and vr fr in Fig. 1 and in Fig. 2 have shown continuation of one of these-trunk lines, line 7" r., to an automatic exchange.--lt is assumed that the -party' at inrcomiminicating; station No, 1 hasfbeen in the act of appropriating trunk line r to which and party first removed his receiver-from its ,switch-hook at his station. By this opera- -tion the'party at station No. 1 included hisl receiver in low resistance bridge of his line so as to guard his line and enable a. busy 4test signal to befurnished to a party seekling his line in a manner which has been described. The calling party endeavm'ing to select the trunk line 7 next fully depresses his key p that is individual to the trunk line in order to test the trunk line. vIt will now be assumed that such trunk line-is idle (a busy test circuit being later traced over a busy trunk line). The seeking party at station No. 1 next releases the actuated button p to permit the spring mechanism thereof.,

to place said key in an intermediate position as shown whereby the calling partys receiver and transmitter are laced in bridge between the sides of the selcted trunk line owing to the energization of the relay .the g cmg left hand winding ofvthis relay g placed in bridge of the line 1 1, all as will readily be understood fromthe previous description-without further explanation, the tour lower contacts of each key p having the same relation with the sides of the trunk line associated therewith as is possessed by the four contacts of each selecting key a with respect to the line associated therewithand also possessing similar circuit relation with respect to the associate relay g. It

may be said that the onlydistinction between the electrical environment of each iie'yj and each key a resides inthe provision of the upper contact for each key "p and certain connections to be mentioned leading from said contact and to the next contact beneath.` With the key p in its intermediate positiom'the trunk line r is arded by the telephone of stat-ion No. 1 bri ged across.

the trunk line and line'No. 1 is uarded by the left hand low resistance win 'ng of the relay at station No. 1 bridged between its sides. Under the assumption that'thetrunk' line is free, the 'calling party at station No. 1 will operate his dial mechanism @'in a well known manner, such dial mechanism being very familiar to those skilled in the art. By

,means of .this 'dial mechanism the wanted part'y shown` at A is selected andl connected with the trunk line'and during the process.

of such connection abridge including the magnet .s and batter t is normally across the sides of the trun line 4in al manner fa-- miliar to those skilled in the art, the elements s and t being present in existing' automatic telephone' exchange equipment. If the party at station No. 1 should desire -or any reason to Adisconnect his telephone from the trunk line and at the same time prevent the operation of the releasing magnet u and male magnet u1, which form other well recognized parts of Aautomatic tele- 50 again placed in bridge of the trunk` line, the

prevent the disconnection of thegcalled 'station A from the trunk line and be in riposi- .lll

tion to resume connection with such trunk line and called station, such partyV at the calling station will fully leleased. selecting keyp and thereafter restore his telephone receiver upon its switchhook andnally permit the said key p to become restored to its'intermediate position. As a vconsequence of these operations relay g at the calling station is'denergized owing to the sepa-ration of the vvcontacts c1. The relay 'v associated with the trunk line is bridged across the sides of the trunk line as a result of the full depression of the key p,

such bridge connection being .traceable from the lower side of the trunk line through the Winding of the 'relay o, the two uppermost contacts of the key p to the upper side of the trunk. The armature of said relay o is attracted s`o as to maintain said bridge' continuous -When the key vp `is finally released, the bridge connection maintainedl by said armature switch being traceable from the 'lower side ofthe trunk line through the Winding of' the relay c, said switch land its contact to the upper side ofthe trunk line. 'lhe bridge including the elements s t having been previously established at the automatic exchange 1n accordance with well A known practice, the circuit for the relay'o 1s maintained closed, and, which is more to the point, the brid e which includes the relay u is maintaine in order that the circuit through the magnet s and battery t may be unbroken during the time that the call- 'ing partys telephone is out of bridge relation with the trunk line so that during this line the releasing nignet u will not, be 0perated at'the callerhylitomatic station but will remain. iu connection with the trunk line. Then the qcalling party desires to resinne the connection of his telephone with the trunk line. he ir-st removes his receiver from its switch-hook, fully depresses the previously actuated-key p and then releases said key to :permit it to occupy an intermediete position. As a consequence of these operations the calling partystelepho'ne is i left hand Winding of the calling partys re- .high resistance,

lay is again -plaoed in bridge of the calling line whereby the telephonie relation of the calling partys telephone with the trunk line is maintained. The relay o, being of say 500 ohms, is nou/shunted bythe calling partys telephone so "that the entire calling and trunk line equipment is restored to that condition which was obtained. when the calling party iirstsecured telephonie connection with the called automatic station.- As I have ill strated the equipment, any station of th intercommunicating system may select a trunk line `v`free for selection,

depress the semi-- ytelephone .each key p having similar control ofthe relay o, of which but one 1s shown to a trunk line, though I do not 'wish to be'limited to the number of these relays. The relays 'v a`re located at onestatlcn' where an attendant operator may be employed for the coming into the intercommunicafting system by Way of the trunk lines and manifested atA the signal devices w in a' manner and by be u iechanism and circuits which need not described, the attendant bein able to elect connection between trunk lines and the wanted lintercommunicating lines. If the trunk line' selected for use by the 'calling party had been busy then such calling party would have received a busy test manifesta.- tion by reason of the circuit established through his telephone receiver which' he had removed from lts switch-hook While holding the actuated button p in its fully depressed position which is the position of any actuated button a or p when a test is' being made of the line individual thereto. test-'circuit then established is well understoodv from the previous description and may be traced from the upper terminal of the battery e through the impedance f, the

armature switch of the calling partys relay g and the normal contact of such switch, the

spring lc* and its alternate contact, back to the battery by way of the device o'for causing the fluctuation of the current flowing from the battery for testing purposes. Such flow of testing current is permitted hand .armature switch ci normal contact Idue to the fact that auch relayg is not energized owing to the presence of the low resistance bridge .established across the trunk line by some other intercommunicating station telephone. 4.

It will be unnecessary to describe the automatic telephone exchange ,equipment as such is well known by those skilled in the art. It is suiiicient to state that the apparatus s hown in association with the trunk purpose ofanswering calls The the switch-hook c, the left' hand lines at the intercommunicating stations cooperates in the manner which has been described-With the magnet .9 and the battery t thatletermine whether or not the releasing magnet u of the automatically operated.

switching mechanism shall release the called automatic line. Inasmuch as I have pro- -vided equipment at the intercommunicating stations for automatically selecting called automatic subscribers I preferably'employ the standard substation equipment in the intercommunicating system such as is furnished by the Automatic Electric Company of'Chicago, Illinois for automatic exchange work, circuit environment being supplied thereto as is illustrated 'and' as has been described. t is understood that such inten of station mechanism or automatic exchange' meclmnism, nor do l Wish to be limited to other precise details of construction and circuit arrangement which have herein shown and .particularly described as changes .may readily be made Without departing from the spirit of my invention. An important feature of my invention however, resides in the fact that I am enabled to hold the trunk line 'r by si circuit established over its metallic sides and without the necessity of employing additional circuits. In oeri tain of the claims I claim the trunk lines broadly as telephone lines, .as my invention is not to be limited to trunk linesr l Having thus described my invention I claim es new and desire to secure by Letters Patent the following:-

1. An intercommunicating telephone system including three or more telephone lines,

' busy test circuit, apparatus et the stations serving partially to establish the busy test circuit and 'common to sind lines, and means for completing the busy test in cooperation with apparatus at the station of the line seeking connection with the line taken for lfuse.

2. An intercommunicating tele hone sys.;

tem including three or more telep one lines,

the stations of said telephone llnes having electro-magnetic mechanisml for connecting station telephones with the telephone li esv of the remaining stations of said lines, a d means brought into operation by lines taken for use for altering the operative condition of the electro-magnetic mechanism at the station of a line seeking connection with' a line taken for use to prevent connection of the telephone at this line seeking station with the line taken for use. 4

An intercommunicating tele hone system including three or more telep one lines, the stations of said telephone lines having electro-magnetic mechanlsm for. connecting station telephones with the telephone lines of the remaining stations of said lines, shunts for the electro-magnetic mechanism, and means brought into operation by lines taken for use for altering the condition of the shunt for the electro-magnetic mechanism at the station of a line seeking connection with a line taken for use to prevent connection of the telephone at this line seeking station with the line taken for use.

In Witness whereof, hereunto subscribe my name thissecond day of November A. D., 1911.

l ELMER n. coRWIN, Witnesses: i

Gn L. CRAGG,

E. L. WHITE. 

